Not applicable.
Not applicable.
The invention is directed to systems for manufacturing die castings and, more particularly to systems for manufacturing die castings configured to measure plural physical parameters during the forming of each die casting and to associate the measured physical parameters with the specific die casting manufactured under those conditions and any defect information subsequently acquired for that die casting. By enabling a die casting manufacturing system to associate such types of information, control over the manufacturing process may be enhanced.
Generally, die castings are produced by forcing a molten metal under pressure into a steel die and maintaining the molten metal under pressure until solidification of the molten metal into a casting is complete. A wide variety of metal and metal alloys may be used in die casting processes. For example, aluminum alloys, brass alloys and zinc alloys are all commonly used in die casting processes to form die castings. Broadly speaking, a die casting process requires the following elements: (a) a die-casting machine to hold a molten metal or metal alloy under pressure; (b) a metallic mold or die capable of receiving the molten metal or metal alloy and designed to permit easy and economical ejection of the solidified metal or metal alloy die casting; and (c) a metal or metal alloy which, when solidified into a metal or metal alloy die casting, will produce a satisfactory product with suitable physical characteristics.
There are two types of die-casting machines commonly in use today. The first, or cold-chambered, die-casting machine forces the molten metal or metal alloy into the die by means of a plunger and chamber located outside of the molten metal or metal alloy bath. Conversely, the second, or hot-chambered, die-casting machine forces the molten metal or metal alloy into the die by means of a cylinder and piston which are submerged in the molten metal or metal alloy bath. Depending on the production requirements therefore, the metallic mold or dies to be used in die casting processes may be constructed in different styles. A xe2x80x9csinglexe2x80x9d die contains an impression of only one part; a xe2x80x9ccombinationxe2x80x9d die contains an impression of multiple parts; a xe2x80x9cmultiplexe2x80x9d die contains two or more impressions of a single part; and a xe2x80x9ccombination-multiplexe2x80x9d die contains a number of impressions of each one of two or more parts. Single dies are comparatively cheap and, since they reduce the tool investment to a minimum for any one part, are typically used for small lot productions. When properly designed, combination dies will reduce the total die cost for a given set of die castings to a minimum. They are particularly useful for die castings that will always be used in the same quantities and formed of the same alloy. Multiple dies are usually slower to operate than single dies but will give higher production rates for the same labor costs.
It should be readily appreciated that a wide variety of die castings may be produced by application of conventional die casting manufacturing principles. One such die casting is an aluminum alloy die casting. Similarly, while aluminum alloy die castings may be used in a wide variety of applications, in one such application, specially shaped aluminum alloy die castings are used as the rocker cover and the rocker housing for the FL Series motorcycle currently manufactured by the Harley-Davidson Motor Company of Milwaukee, Wis. To enhance the appearance thereof, prior to mounting of the rocker cover and rocker housing die castings on the FL Series motorcycle, the aluminum alloy die castings are plated with chromium. Traditionally, the aluminum alloy die castings have been manufactured at a first facility and subsequently shipped to a second facility for plating.
A drawback to this process has been that, once subjected to the chrome-plating process, the aluminum alloy die castings produced at the first facility often proved unsuitable for their intended later use. For example, using conventional die casting techniques, chrome-plated aluminum alloy die castings to be used as either a rocker cover or rocker housing for the aforementioned FL Series motorcycles were experiencing a rejection rate of about 40% due to defects noted during inspections of the die castings conducted during and/or after the chrome-plating process. While the rejection rate has been attributed to a variety of causes, one such cause is that a number of the various types of defects which commonly occur during the manufacture of an aluminum alloy die casting can remain unnoticed until after an attempt has been made to chrome-plate the die casting.
It should be readily appreciated that a rejection rate of about 40% adds considerably to the cost of chrome-plated aluminum alloy rocker covers or chrome-plated aluminum alloy rocker housings. It should also be readily appreciated that substantial cost savings may be achieved by reducing the rejection rate of chrome-plated aluminum alloy rocker covers, chrome-plated aluminum alloy rocker housings and other products manufactured using die casting processes which are currently plagued by high rejection rates. Achieving a reduction in such rejection rates is, therefore, an object of the present invention.
In one embodiment, the present invention is directed to a system for manufacturing metal or metal-alloy castings which includes a die for forming the metal or metal-alloy castings and plural sensors, for measuring the level of various physical parameters during the manufacture of each casting. The system further includes means, for example, a pin stamp for marking each casting formed by the die with a unique identifier and a computer system, coupled to the sensors and the pin stamp or other marking means, for recording the level of each physical parameters each time a casting is formed by the die and associating the recorded levels with the unique identifier marked on that casting.
In one particular aspect of this embodiment of the invention, the system for manufacturing metal or metal-alloy castings further includes a test station for examining the formed metal or metal-alloy castings for defects and a user interface coupled to the computer system. Using the unique identifier marked on each casting, the computer system associates defect information acquired at the test station and input the computer system via the user interface with the levels of the physical parameters recorded during formation of that casting.
In further aspects of this embodiment of the invention, the sensors may variously include at least one temperature sensor (or as many as four temperature sensors) for measuring temperature of the die during formation of the castings, a pressure sensor for measuring pressure within a cavity formed by interior side surfaces of the die, a first data collector for collecting data related to each shot of molten metal or molten metal-alloy injected into the die cavity by a shot/sleeve plunger system coupled to the die, a second data collector for collecting data related to each spray of a lubricant onto interior side surfaces of the die prior to each shot of molten metal or molten metal-alloy into the die cavity, a temperature sensor for measuring the temperature of the molten metal or molten metal-alloy held by a secondary furnace which supplies the molten metal or molten metal-alloy to the shot/sleeve plunger system, a spectrometer for determining the chemical composition of the molten metal or molten metal-alloy held by a primary furnace which supplies the molten metal or molten metal-alloy to the secondary furnace, a temperature sensor for measuring the temperature of heated oil circulated through recirculation channels formed in the die by an oil circulation system. In these various aspects, the computer system records the data related to die temperature, cavity pressure, die shot, pre-shot die lubrication, molten metal or metal-alloy temperature and/or molten metal or metal-alloy composition and associates the data with the unique identifier marked on the casting during the formation thereof.
In still further aspects of this embodiment of the invention, the system includes a user interface coupled to the computer system, a polish station for polishing the metal or metal-alloy castings formed by the die and/or a plating system for plating the metal or metal-alloy castings formed by the die. In these aspects of the invention the computer system uses the unique identifier marked on each metal or metal-alloy casting to associate defect information acquired at the polish and/or plating station with the levels of the physical parameters recorded during formation of that metal or metal-alloy casting.
In further embodiments thereof, the present invention is directed to computer systems configured for use in die casting manufacturing processes. The computer systems include a processor subsystem and a memory subsystem coupled to the processor subsystem by a bus subsystem. Residing in the memory subsystem and executable by the processor subsystem is a first software application. In one such embodiment, the first application is configured to assemble casting profiles from physical parameters measured during formation of each one of a plurality of castings, a unique identifier marked on each one of the plurality of castings during the formation thereof and defect information acquired during post-formation analysis of each one of the plurality of castings. In another such embodiment, the first application is configured to assemble casting profiles from a plurality of physical parameters measured during formation of each one of a plurality of castings and a unique identifier marked on each one of the plurality of castings during the formation thereof. Once assembled, the casting profiles, which may include acceptable casting profiles and unacceptable casting profiles, are maintained in a data space of the memory subsystem.
In further aspects of these embodiments of the invention, the computer system further includes a second software application which also resides in the memory subsystem and is executable by the processor subsystem. Variously, the second software application may compare the plurality of physical parameters measured during subsequent formations of castings to the plurality of physical parameters included in the acceptable and unacceptable casting profiles and issue notifications if the subsequently measured plurality of physical parameters match the plurality of physical parameters included in an unacceptable casting profile or may examine the casting profiles assembled by the first software application and, based upon the examination of the casting profiles, issue instructions, to a controller of an automated die cast cell used in the manufacturing process to form the castings, to modify at least one of the plurality of physical parameters.